Mask Rib Dimension Control via Edge Etching
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Solution Overview
Problem
The manufacturing of masks with high-accuracy fine patterns for high-density semiconductor devices and high-resolution flat panel displays is challenging due to difficulties in forming final ribs with desired dimensions and structures, which can lead to pattern failures and deformation.
Innovation Solution
A method involving multiple photolithography processes to form initial ribs and then remove upper edge portions to create final ribs with mirror-symmetric trapezoidal sections, including linear and curved sidewalls, using photoresist patterns as etching masks, and isotropic etching processes to achieve the desired shape and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography processes are used to form ribs directly with final dimensions, then the manufacturing process is simple, but the manufacturing precision of fine patterns deteriorates due to inability to achieve desired rib dimensions and shapes
Solution Approach 1:
The formation of ribs is divided into multiple stages: first forming initial ribs with larger dimensions using a first photolithography process, then selectively removing upper edge portions through additional photolithography and etching processes to achieve the final precise dimensions. This segmentation allows each stage to optimize for its specific purpose, achieving high precision without excessive overall complexity.
Solution Approach 2:
Initial ribs are formed in advance with dimensions larger than the final required dimensions. This preliminary structure serves as a precursor that can be subsequently refined. The upper edge portions are then removed to achieve the final precise dimensions, allowing the process to work backwards from a simpler initial state to the precise final state.
2Manufacturing precision
If multiple photolithography processes are used to form initial ribs and then remove upper edge portions, then the manufacturing precision of fine patterns is improved, but the device complexity increases
Solution Approach 1:
Different regions of the mask substrate receive different treatments at different stages. The upper edge portions of initial ribs are selectively removed while preserving other regions. Photoresist patterns are applied locally to specific areas to control the etching process, allowing precise local modification of rib structures without affecting the entire mask uniformly.
Solution Approach 2:
The process transitions from two-dimensional photoresist patterning to three-dimensional rib structure formation, then back to two-dimensional refinement by removing upper edge portions. This dimensional transition allows the creation of complex rib profiles with controlled top widths and sidewall shapes that cannot be achieved with simple planar photolithography alone.
3Productivity
If direct etching is used to form ribs with final dimensions, then the process is fast and simple, but the reliability of pattern transfer deteriorates due to pattern failures and deformation
Solution Approach 1:
Initial ribs are formed in advance as a robust preliminary structure that is less susceptible to process variations. This preliminary structure provides a stable foundation that can withstand subsequent processing steps. The final precise dimensions are then achieved by selective removal of upper edge portions, ensuring pattern reliability without requiring the entire process to occur in a single critical step.
Solution Approach 2:
The multi-stage process with intermediate structures provides a buffer against process variations and errors. If issues arise during the formation of initial ribs, the larger dimensions provide a margin of error. The subsequent selective removal process allows for fine-tuning and correction, cushioning against potential pattern failures that would occur in a single direct etching step.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the production of masks with high-accuracy fine patterns that meet technical requirements for miniaturization, preventing deformation and ensuring the transfer or deposition of high-resolution patterns, thus satisfying the needs for high-density semiconductor devices and high-resolution flat panel displays.
Implementation Method 1
forming a first photoresist pattern on a top surface of the mask substrate, forming a second photoresist pattern on a bottom surface of the mask substrate, forming an upper photoresist pattern on top surfaces of the initial ribs
Implementation Method 2
etching the top and bottom surfaces of the mask substrate using the first and second photoresist patterns as etching masks to form first and second recesses, etching the mask substrate using the first, second and third photoresist patterns as etching masks to form a through hole
Data Source
AI summary
A method of manufacturing a mask may include forming initial ribs and removing edge portions of the initial ribs to form final ribs, each of which has a top width smaller than that of the initial rib. A space between the initial ribs may be smaller than a width of a slit limited by the final ribs.